1. Field of the Invention
The present invention relates to an image pickup apparatus and an image pickup method capable of acquiring image data for still image recording and image data for image display.
2. Description of the Related Art
Image pickup apparatuses such as digital cameras and digital video cameras are mounted with an image pickup device that converts an optical image to an electric signal, and the market share of image pickup devices is shifting from CCD to CMOS in recent years.
A MOS-type image pickup device such as CMOS mounted in an image pickup apparatus is designed to sequentially read charge of many pixels which are two-dimensionally arrayed on an image pickup surface, but an exposure start time and an exposure end time in this condition differ from one pixel to another (from one line to another). Thus, a MOS-type image pickup device configured to be able to equalize exposure start times of all pixels and equalize exposure end times of all pixels (that is, configured to be able to perform control using a global shutter) has a configuration including a photoelectric conversion section such as a photodiode that generates a signal according to an exposure amount, a signal storage section that temporarily stores signal charge generated in the photoelectric conversion section and further a transistor that functions as a switch when transferring or resetting charge.
One example of pixel configuration of such an image pickup device is a configuration shown in FIG. 3 according to an embodiment of the present invention provided with five transistors within one pixel. The configuration shown in FIG. 3 allows control through a global shutter using a signal storage section FD as an in-pixel memory. When this image pickup device is used for a digital camera, for example, Japanese Patent Application Laid-Open Publication No. 2005-65184 describes a technique of driving the image pickup device to suppress KTC noise (reset noise) according to the following sequence.
(1) The signal storage section FD is reset by a transistor Mr and the reset data is read line by line through sequential scanning and stored.
(2) Photoelectric conversion sections PD of all pixels are collectively reset and pixel data of the photoelectric conversion sections PD are collectively transferred to the signal storage sections FD after a lapse of a predetermined exposure time.
(3) The pixel data transferred to the signal storage sections FD is read line by line through sequential scanning and the reset data stored in (1) is subtracted therefrom (a difference is calculated).